Torque converters generally comprise an externally powered driving member, known as a pump, and a driven member, known as a turbine, each having the shape of a torus. The two members are coaxially mounted in a housing for independent rotation and have blade-supporting peripheral walls jointly defining a toroidal space filled with transmission fluid hereinafter referred to as oil. This toroidal space is also bounded, along a peripheral zone closest to the axis of rotation, by blade-supporting walls of a so-called stator which, however, generally is not stationary but is free-wheeling in the housing to serve as a return guide for the oil circulating within that space between the blades of all three members. In the system here contemplated, some of the oil is continuously drained off to a sump and, after cooling in an external circuit, is returned to the converter by a supply pump. Certain converters operating according to this principle are known under the designation Trilok.
Conventionally, the fresh oil is admitted into the toroidal converter space through an inlet which terminates in a channel passing through the hub of the pump member and opens into the torus thereof while the spent oil is removed from the torus of the turbine member through an outlet partly passing through the hub of the latter. Though this arrangement has certain structural conveniences, it sets the relatively cold incoming oil in immediate rotation at substantially the speed of the pump member and centrifugates it, on account of its greater specific gravity, toward the periphery of the toroidal converter space whence most of it promptly flows to the outlet and thus to the sump. The externally cooled oil, therefore, mingles only to a minor extent with the hotter oil circulating in the converter space whereby the heat generated in the converter, which may be particularly intense with repeated starts and stops of a vehicle using same, is dissipated only at a slow rate. It thus often becomes necessary, in order to prevent overheating, to use outsize supply pumps and coolers for the recirculation of a sufficient amount of oil.